Exploring the relationship between parental relatedness and male reproductive success in the Antarctic fur seal Arctocephalus gazella

Recent genetic studies of natural populations have shown that heterozygosity and other genetic estimates of parental relatedness correlate with a wide variety of fitness traits, from juvenile survival and parasite resistance to male reproductive success. Many of these traits involve health and survival, where the underlying mechanism may involve changes in the effectiveness of the immune system. However, for traits such as reproductive success, the likely mechanisms remain less obvious. In this paper, we examine the relationship between heterozygosity and a range of traits that contribute to male reproductive success, including time spent on territories and competitiveness. Our analysis is based on observational and genetic data from eight consecutive breeding seasons at a colony of the Antarctic fur seal, Arctocephalus gazella. Overall, male reproductive success was found to correlate strongly with internal relatedness (IR, a form of heterozygosity). When different components of success were analyzed, we found that IR correlates independently with reproductive longevity, time spent ashore, and competitive ability per unit mating opportunity on the study beach, with more heterozygous males being more successful. Behavioral observations were sufficiently detailed to allow examination of how daily mean IR values for males present on the beach varied within seasons and from year to year. Again, significant variation was found both among and within seasons, with more homozygous males appearing less able to hold territories in poor seasons when pup production is low and, within a season, at both the start of the season and to some extent around the peak of female estrus. Finally, we tested whether the benefits of high heterozygosity are due mainly to a genomewide effect (e.g. inbreeding depression) or to single locus heterosis by asking whether the relationship between IR and male success was robust to the removal of any single locus or to any pair of loci. Since the relationship remained significant in all cases, we favor a multilocus explanation for the effects we report.     

High incidence of Atlantic salmon × brown trout hybrids in a Lake District stream

Hypervariable minisatellite DNA single-locus profiling and mitochondrial DNA analysis revealed that 18.48% of juvenile Atlantic salmon Salmo salar in Troutbeck, a stream in the R. Leven catchment of the English Lake District, were hybrids between Atlantic salmon and brown trout S. trutta , and that hybridization was bidirectional.     

Brothers smell similar: variation in the sex pheromone of male European Beewolves Philanthus triangulum F. (Hymenoptera: Crabronidae) and its implications for inbreeding avoidance

Female choice is thought to increase the fitness returns of females. The complementary choice model states that the best mate depends on the particular genotype of a female. Aculeate Hymenoptera represent a special case of complementary female choice because males should be chosen on the basis of their allele at the sex determination locus. The prevalent sex determination mechanism in bees and wasps (single-locus complementary sex determination) requires that, to produce a daughter, diploid offspring are heterozygous at the sex determination locus. Otherwise, infertile diploid males result. Inevitably, the proportion of diploid males increases with the rate of inbreeding. In the European Beewolf, males scent mark territories to attract mates and the composition of the pheromone might provide a basis for female choice. One crucial prerequisite for females to be able to discriminate against brothers and avoid inbreeding is that the male sex pheromone varies with familial affiliation. This hypothesis was tested by analysing the pheromone of male progeny of eight mothers using gas chromatography and mass spectrometry. A significantly higher similarity was found among brothers than among unrelated individuals. Such a genetic component of a male sex pheromone has not yet been described from aculeate Hymenoptera.  © 2006 The Linnean Society of London, Biological Journal of the Linnean Society , 2006, 89 , 433–442.     

Charomid cloning vectors meet the pedipalpal chelae: single-locus minisatellite DNA probes for paternity assignment in the harlequin beetle-riding pseudoscorpion

We describe the first application of the charomid-cloning method for developing single-locus minisatellite DNA probes in a terrestrial arthropod. From a genomic library of the neotropical pseudoscorpion, Cordylochernes scorpioides , we have isolated two probes with heterozygosities exceeding 95%. These probes yielded single-locus patterns after only low stringency washing and in the absence of genomic competitor DNA. Analysis of three pedigrees indicated germline stability and showed no evidence of linkage between the loci. Patterns of allelic transmission generally conformed closely to Mendelian expectations but large offspring numbers did enable detection of one example of significant bias in allele inheritance. Two test cases are presented to illustrate the clarity and power with which these probes can establish paternity: (i) a female mated to three unrelated males, and (ii) a female mated to two of her brothers. In both cases, a single probe could be used to assign the paternity of all offspring.     

The evolving technology of DNA fingerprinting and its application to fisheries and aquaculture

In 1985, Alec Jeffreys reported the development of multilocus DNA fingerprinting by Southern blot-detection of hypervariable minisatellites or variable number of tandem repeat (VNTR) loci. This technology found immediate application to various forensic and scientific problems, including fisheries and aquaculture. By 1989, however, it was recognized by many researchers that inherent problems exist in the application of multilocus fingerprinting to large sample sizes as might occur in fisheries and aquaculture genetic studies. As such, individual VNTRs were cloned for single-locus DNA fingerprinting. Although single-locus fingerprinting ameliorates many of the problems associated with multilocus DNA fingerprinting, it suffers from the problem that electrophorectic anomalies of band migration within and between gels necessitates binning of alleles, thus underestimating genetic variability in a given population. Amplification of microsatellite loci by the polymerase chain reaction, however, solved many of the problems of Southern blot-based DNA fingerprinting. Moreover, microsatellites exhibit attributes that make them particularly suitable as genetic markers for numerous applications in aquaculture and fisheries research: (1) they are abundant in the genome; (2) they display varying levels of polymorphism; (3) alleles exhibit codominant Mendelian inheritance; (4) minute amounts of tissue are required for assay (e.g., dried scales or otoliths); (5) loci are conserved in related species; (6) potential for automated assay. Recent innovations in DNA fingerprinting technology developed over the past 5 years are discussed with special emphasis on microsatellites and their application to fisheries and aquaculture, e.g., behavioural and population genetics of wild species, and selection and breeding programmes for aquaculture broodstock.